Today, Signaling System 7 (SS7) includes almost all of the voice-based applications supporting supplementary voice services and mobility/roaming services provided by the wireless operators. Present SS7 signaling is transported exclusively over the SS7/PSTN (Public Switched Telephone Network) using the SS7 transport protocols, namely MTP3/2/1, over T1/E1 lines. There is a vast SS7 installed base in both wire-line and wireless networks. These networks are reliable but relatively expensive and less flexible than Internet protocol (IP)-based networks. Thus, industry is seeking to replace the SS7 transport protocols with IP.
To this end, the SIGTRAN working group of the Internet Engineering Task Force (IETF) has been focused on the transport of packet-based PSTN signaling over IP networks, defining a number of SS7/IP user adaptation protocols including M2UA, M3UA, IUA, and SUA. Two of the key problems encountered when developing SS7/IP user adaptation protocols are discovering the appropriate service application node for messages and efficiently routing and interfacing with the legacy SS7 networks. Certain mobility services such as the registration of a mobile subscriber, for example, pose a special challenge. As in the mobile environment, it is the International Mobile Station Identifier (IMSI), assigned in accordance with the International Telecommunications Union (ITU) E.212 standard, that is used for registering and authenticating a subscriber, rather than an E.164 number. Therefore, in order to provide mobility services and common, E.164-number-associated services (such as a simple phone call, short message service (SMS), etc.), two separate domain name service (DNS)-based database, storage, routing, and administration schemes would presently need to be deployed, one based on E.164 (e.g., using the ENUM service (per the IETF standard RFC 2916)) and another based on E.212/DNS, not to mention other domains that might need to be added depending on the services associated with other global titles (GTs). Moreover, such a solution would be proprietary and would not likely be widely accepted.
Alternatively, the translation of the GT Information to an IP address could be done using common, external services such as those provided by ENUM/DNS servers. However, for ENUM (DNS) to be used for mapping mobile numbers to IP addresses we need to define a unique domain for each numbering plan (e.g, e164.arpa, e212.arpa, and e214.arpa). In addition to creating new domains by the Internet Assigned Numbers Authority (IANA), there is tremendous work that would need to be done to develop the procedures to administer a massive database of all of the E.164/212/214 numbers. Each of these numbers would need to be mapped to the IP address corresponding to the appropriate SS7 node in the appropriate operator's system (operators may have multiple SUA nodes as they scale their systems). Thus, a common solution based on ENUM/DNS, e.g., that does not require the administration of all of the E.164/212/214 numbers to provide service discovery and service node identification (i.e., retrieval of the destination IP address) would be preferred over those presently proposed. Therefore, a need exists for an apparatus and method enabling such a solution for SS7/IP communication.